Infants Fed Peanut, Egg, and Milk Were Less Likely to Develop Sensitization to the Foods

Peanut sandwiches
Students at Escondido Charter High School work to set a world record by using the most flavors of peanut butter and jam on a previous National Peanut Butter and Jelly Day. New data show that the earlier highly allergenic foods like peanuts are offered to infants the less likely they are to develop food sensitization to the foods by age 1. Mike Blake/Reuters

For children with food allergies, life isn't always so sweet. Monitoring these allergies to avoid serious, potentially fatal, reactions can take the joy right out of ice cream cones and birthday cake. Parents would be wise to do anything possible to help their child avoid the worry and burden that accompanies a food allergy diagnosis. A new study is the latest to show that the earlier children are fed highly allergenic foods, the less likely they are to develop the food sensitization to them that is considered a precursor to food allergy.

Research currently being prepared for publication and presented at the American Thoracic Society's international conference this week showed infants who were given cow's milk products, egg or peanut butter early on were less likely to develop sensitization to the foods when assessed at age 1. Parents who fed their infants eggs reduced their child's risk of developing sensitization not only to eggs, but to any of the three foods.

Previous studies have assessed whether older children who had been fed highly allergenic foods in infancy developed sensitization or allergy later in childhood or focused on children already believed to be at risk of developing food allergy. This study is thought to be the first to involve children who were not suspected of food sensitization or allergy.

Researchers working on the Canadian Healthy Infant Longitudinal Development Study questioned parents of 1,421 Canadian children when their infants reached 3, 6, 12, 18, and 24 months on when they had introduced egg, peanut butter and cow's milk products to their children's diets; which allergenic foods were introduced simultaneously; and whether the children were exclusively breast-fed until 6 months. Nearly half introduced cow's milk products, including infant formula based on cow's milk, to their children before six months. About 6 percent introduced eggs before 6 months and 76 percent did so between 7 and 12 months. Just 1 percent of parents introduced peanuts before 6 months and 41 percent did so between 7 and 12 months.

At age 1, the children underwent skin prick testing to assess whether they had developed sensitization to any of the three foods. During this test, a drop of solution containing the food allergen is placed on a patient's forearm or back. Using a small plastic probe or needle, the doctor or nurse will prick or scratch the skin to allow a tiny amount of the solution to enter just below the skin's surface. A raised white bump surrounded by a small circle of itchy red skin indicates food sensitization.

The researchers found that, overall, however, there was a trend of protective benefits when the tested foods were introduced before age 1 compared to food avoidance during an infant's first year. Most impressively, parents who fed their babies eggs before age 1 reduced their risk of sensitization to any of the three foods. Exclusive breast feeding until six months did not affect the infant's risk of being sensitized to egg or peanut, but was shown to increase the risk of sensitization to cow's milk products.

While the research team isn't certain what to make of the protective effect eggs had on preventing sensitization to other allergenic foods, says lead researcher Maxwell Tran, a research student at McMaster University in Hamilton, Ontario, "It's possible that parents who introduce eggs before age 1 might be the parents who tend to introduce other foods before age 1."

Tran believes their findings will reinforce the move already underway among physicians around the world advising parents to introduce allergenic foods in infancy rather than delay according to previous guidelines. By now, most parents of young children are aware they should no longer delay giving their children peanuts until age 3, a recommendation that was in effect from 2000 until 2008 intended to reduce diagnoses of peanut allergy, which is the most common cause of food-related death, according to the Centers for Disease Control and Prevention. That's not what happened, however; instead peanut allergy diagnoses quadrupled between 1997 and today. A couple of studies exposed the error of the American Academy of Pediatrics's recommendations. One, published in 2008, found the rate of peanut allergy in Israeli children was only about one-tenth that of Jewish children in Britain. The researchers' best guess was that this was because British parents avoided giving peanuts while Israeli infants consumed high amount of peanut protein in the first year of life. A 2015 study found that children deemed as infants to be at high risk of developing peanut allergy were less likely to actually develop the allergy by age 5 when their parents fed them peanuts than when they did not. Both studies impacted new recommendations in many parts of the world on when to introduce allergenic foods.

"The clinical implications of our findings are that early introduction of allergenic foods (egg, cow's milk products, and peanut) before age 1 should be encouraged and is better than food avoidance for reducing the risk of food sensitization," says Tran. "Many guidelines around the world are now reflecting this shift, with the recommendation of food introduction before 6 months of age."

One caveat is that this study looked at food sensitization, and not food allergies. Food allergies can only be diagnosed for sure with an oral food challenge performed by administering measured doses of an allergenic food to see if it triggers symptoms in a patient. Often allergists don't go to this extent, especially with young children, and instead assess patients who have had reactions to allergenic foods by skin prick and blood testing for food sensitization. Although these are not the gold standards for food allergy diagnosis, in patients who have had severe reactions to allergenic foods whose skin prick and blood test results are positive, food allergy is considered highly likely. "Sensitization is not the same as allergy, but it is an important step on the pathway," says Tran. Patients with food sensitization are advised to avoid the allergenic foods. Allergists typically then prescribe emergency treatment measures for severe reaction that can accompany accidental exposure to the allergen.